They are not going to invest that much to bring in good players for the squad. Because simply, if they spend that much there will probably not be able to make that by selling players. So even though right now, it is easy to make money by selling players, if the player has some talent, they are still not taking the risk.
However, it is their business model. They can do whatever they feel like working in favour of them. But they are definitely not going for glory. They are going for the Money. And that is the biggest problem, in my opinion. at least from the perspective of a spectator.
That's why clubs held by rich people from Saudi Arabia are much better because they not only expect profits from selling players, but they also focus on purchasing the players needed by the club. Club profits are not the only way from selling players and there are many other things they can do. If the club does not have good achievements and does not have great players then sponsorship, ticket sales, merchandise sales and so on cannot be achieved. Because the number of people who see the club will be very limited and there is nothing special about the club seen by people other than fans.
That's the problem that Dortmund management must solve because they basically have big names. Bayern Munich's only strong challenger is actually Dortmund, but they don't try to improve the quality of their game by bringing in good players, so in the end they still can't compete with Bayern Munich.